I have an 02 silverado that has developed a fairly strange noise under the hood. Only when I am running the fan on the cool side, or running the A/C. Typically I can hear it and feel it through the throttle, and back off for a second or two, it normally goes away. I suspect the A/C clutch, or a belt possibly, but if it was the belt, it would probably squeal rather than ratchet. The strange thing is that if I am only using cool air and do not have the AC toggled 'on' it still does it. So I am given to put some thought into it, and I am not mechanically inclined beyond tuneups and oil changes. There is absolutely no evidence of any kind of fan blade rub or impact anywhere to be found, which is probably a better example of the noise being made, like the blade is hitting the shroud. More throttle, faster noise, off the gas, it comes down with the rpm, and as the rpm drops below about 1000 on the tach it stops...

Any thoughts or guidance would be very welcomed!

 

First thing I would look at is driver side motor mount.

 

Thanks for the input. I have checked this lead, and everything appears to be fine. The motor doesn't 'jump' or lift when the throttle is advanced. There is no visible damage to the mount's themselves and the bolts too. Any other suggestions?

Appreciate the help!